Growth parameters
The growth performance of fodder maize, in terms of plant height, number of leaves per plant and leaf-to-stem ratio (LSR), was markedly enhanced by the foliar application of Nano urea plus and Nano ZnO. These parameters, essential for assessing vegetative growth, biomass accumulation and forage quality, demonstrated significant improvements with the application of Nano nutrients. Table 1 presents the data on growth parameters recorded at the harvest stage in fodder maize during the two years. The foliar application of 1% Nano Urea Plus combined with 100 ppm Nano ZnO (T
8) recorded maximum mean plant height, number of leaves per plant and leaf stem ratio of 297.25 cm, 13.78 and 0.44 respectively. These parameters were statistically comparable to the combination of 1% Nano Urea Plus and 50 ppm Nano ZnO (T
7). In contrast, the absolute control, devoid of any fertilizer application (T
1), exhibited the shortest mean plant height (212.38 cm), lowest leaf count (10.93) and lowest LSR (0.28). These physiological improvements contribute to increased plant height and overall plant vigor. The increase in the number of leaves per plant and LSR might be attributed to enhanced nitrogen availability and its pivotal role in chlorophyll formation and protein synthesis, promoting leaf expansion and canopy development while zinc aids in auxin synthesis, boosting leaf proliferation and vegetative growth. The results of this study align with previous research in maize
(Parameshnaik et al., 2024).
Performance of green and dry fodder yield
The results demonstrated a significant increase in both green fodder yield (GFY) and dry fodder yield (DFY) with the application of Nano Urea Plus and Nano ZnO compared to the control and recommended dose of fertilizers and are presented in (Fig 1). Among the treatments, foliar application of 1% Nano Urea Plus + 100 ppm Nano ZnO (T8) recorded the highest mean GFY (437.04 q ha
-1) and DFY (101.7 q ha
-1), which was statistically on par with 1% Nano Urea Plus + 50 ppm Nano ZnO (T
7), producing 431.58 q ha
-1 and 97.94 q ha
-1 of GFY and DFY, respectively. The lowest mean GFY and DFY of 300.70 q ha
-1 and 37.08 q ha
-1 recorded with no application of fertilizers. The GFY showed an increase of 45.34% and 17.42% respectively compared to the treatments of no application of fertilizers and recommended dose of fertilizers (T
1). Nano-sized urea has improved leaf penetration, increasing the nutrient uptake and efficiency of its use. It boosts chlorophyll content, photosynthate and cell division, promoting vigorous growth and higher green fodder yield in maize (
Rajesh et al.,2022). Zinc acts as a co-factor for various enzymes involved in carbohydrate, protein and auxin metabolism, while also maintaining membrane integrity
(Gonzalez et al., 2019). The significant increase in fodder yield in plants treated with 1% Nano Urea Plus + 100 ppm Nano ZnO (T
8) is owing to enhanced nitrogen use efficiency and improved micronutrient availability, promoting vigorous vegetative growth and biomass accumulation. These results agree with recent studies that highlight the effectiveness of nano fertilizers in improving maize productivity
(Kashyap et al., 2023).
Forage quality parameters
Effect on crude protein, crude protein yield, total ash and ether extract
Crude protein (CP), ether extract (EE) and total ash
(TA) were significantly influenced by different treatments. The data related to effect of Nano Urea Plus and Nano ZnO in fodder maize is given in Table 2. The maximum CP (9.7%) and CPY 9.91 q ha
-1 were recorded in the foliar application of 1% Nano Urea Plus + 100 ppm Nano ZnO (T
8). However, it was found statistically on par with the foliar application of 1% Nano Urea Plus + 50 ppm Nano ZnO (T
7) while the lowest values of CP (6.93%) and CP (2.57 q ha
-1) were observed in the absolute control (T
1).
The application of Nano Urea Plus and Nano ZnO considerably impacts the EE and TA content in fodder maize. Among the treatments, the highest mean EE (2.56%) was recorded with the foliar application of 1% Nano Urea Plus and 100 ppm Nano ZnO (T
8), followed closely by (T
7) 1% Nano Urea Plus and 50 ppm Nano ZnO (2.44%). In contrast, the lowest EE content (1.31%) was observed in the control treatment (T
1), which did not receive any fertilizer application. Similarly, the maximum mean TA (9.19%) was observed in the treatment with 1% Nano Urea Plus and 100 ppm Nano ZnO (T
8), which was statistically comparable to 1% Nano Urea Plus and 50 ppm Nano ZnO (8.99%) (T
7). On the other hand, the lowest TA (6.85%) was recorded in the control treatment (T
1). EE represents the lipid content of fodder and plays a crucial role in enhancing the energy density and digestibility of animal feed. Ether extract referred to as crude fat, can serve as a concentrated energy source for livestock growth, maintenance and overall performance. However, the digestibility of EE varies among different feed sources, directly impacting nutrient absorption, weight gain and feed conversion ratios in cattle, as energy-rich concentrates support better growth rates
(Liman et al., 2023).
The increased TA content observed in T
8 may be attributed to the enhanced accumulation of essential minerals such as phosphorus, potassium, copper and manganese, facilitated by the positive interaction of zinc with nitrogen and its role in improving mineral uptake in plants
(Rajendra et al., 2016). Higher mineral concentrations in fodder directly contribute to improved livestock nutrition by supporting vital physiological functions, bone development, enzyme activation and overall metabolic health, ultimately leading to better growth performance, reproductive efficiency and disease resistance in animals.
Effect on fibre fractions
The application of higher concentrations of Nano Urea and Nano ZnO led to a slight decrease in crude fibre (CF) content. The minimum CF of 28.95% was recorded in T
8, while the maximum CF of 36.67% was observed in T
1. The significant reduction in fibre fractions, including acid detergent fiber (ADF), neutral detergent fiber (NDF) and acid detergent lignin (ADL), were noted in treatments receiving higher concentrations of foliar nano-fertilizers (Table 3). Specifically, the lowest ADF (36.66%), NDF (57.56%) and ADL (5.01%) were observed in plants treated with 1% Nano Urea Plus and 100 ppm Nano ZnO (T
8). This was comparable to the treatment with 1% Nano Urea Plus and 50 ppm Nano ZnO (T
7). Conversely, the highest values for ADF (45.91%), NDF (69.44%) and ADL (6.42%) were found in the absolute control treatment (T
1). These results suggest that the application of Nano Urea Plus and Nano ZnO reduces fibre fractions in fodder maize, likely due to the enhanced nutrient uptake and utilization efficiency enabled by the nano fertilizers. The higher fibre content in T
8 could be attributed to the structural development of plant tissues, which is enhanced by balanced nutrient availability
(Dey et al., 2024). Moreover, the foliar application of nano-fertilizers likely contributed to the robust formation of cell walls, which may explain the increased crude fibre content. Interestingly, the hemicellulose (HC) content remained non-significant among the treatments across both seasons. The effect of Nano Urea Plus and Nano ZnO in ADF, fodder maize is shown below (Fig 1). The data related to CPY and CFY is furnished in (Fig 1).
Bhaumik and Rajeev (2024) reported similar findings, noting an increase in CF, ADF, NDF and ADL contents in fodder maize treated with Nano Urea and Nano ZnO. Studies have also shown that lower NDF levels in animal diets can significantly enhance the digestibility of dry matter (DM) and organic matter (OM) in cattle (Truong and Tuan, 2023). In ruminants, reduced fibre levels contribute to more efficient rumen fermentation, leading to higher volatile fatty acid production and better nitrogen utilization
(Zhou et al., 2022). Thus, the application of nano-fertilizers not only improves crop quality but also has potential benefits for animal nutrition by increasing feed digestibility and enhancing nutrient absorption.